What describes crackles (rales)?

• A. Continuous, high-pitched whistling sounds
• B. Discontinuous, brief, popping, or crackling sounds
• C. Low-pitched, snoring sounds
• D. Grating or creaking sound

Answer: (B)

Crackles are discontinuous, brief, popping or crackling sounds heard with auscultation, usually during inspiration. They occur when small airways or alveoli pop open or when air bubbles through fluid in the airways. This brief, noncontinuous quality is what sets crackles apart from other lung sounds.

By contrast, continuous, high-pitched whistling sounds describe wheezes, which come from narrowed airways. Low-pitched, snoring sounds describe rhonchi, typically due to secretions in larger airways. A grating or creaking sound describes a pleural friction rub, from rubbing of inflamed pleural surfaces.